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  • Why am I getting a Java NoSuchPortException when the port exists?

    - by user258526
    Got the following production code below, I'm using it for a new driver. portName is COM4 and this port exists on the PC (and I can connect to it with hyperterminal), so why does Javacomm throw a NoSuchPortException? COM4 shows up fine in device mgr. too final String portName = getSerialPort(); try { final CommPortIdentifier id = CommPortIdentifier.getPortIdentifier(portName); port = (SerialPort) id.open(getName(), 1000); } catch (NoSuchPortException nspe) { report(SeverityCode.LEVEL2, getName(), "PIN Pad is not connected to " + portName + " port, or the port does not exist."); return; } catch (PortInUseException piue) { report(SeverityCode.LEVEL2, getName(), portName + " port is already in-use by some other device. Reason: " + piue.getMessage()); return; }

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  • How should I map an abstract class with simple xml in Java?

    - by spderosso
    Hi, I want to achieve the following xml using simple xml framework (http://simple.sourceforge.net/): <events> <course-added date="01/01/2010"> ... </course-added> <course-removed date="01/02/2010"> .... </course-removed> <student-enrolled date="01/02/2010"> ... </student-enrolled> </events> I have the following (but it doesn't achieve the desired xml): @Root(name="events") class XMLEvents { @ElementList(inline=true) ArrayList<XMLEvent> events = Lists.newArrayList(); ... } abstract class XMLEvent { @Attribute(name="date") String dateOfEventFormatted; ... } And different type of XMLNodes that have different information (but are all different types of events) @Root(name="course-added") class XMLCourseAdded extends XMLEvent{ @Element(name="course") XMLCourseLongFormat course; .... } @Root(name="course-removed") class XMLCourseRemoved extends XMLEvent { @Element(name="course-id") String courseId; ... } How should I do the mapping or what should I change in order to be able to achieve de desired xml? Thanks!

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  • How can two programs talk to each other in Java?

    - by Arnon
    I want to ?reduce? the CPU usage/ROM usage/RAM usage - generally?, all system resources that my app uses - who doesn't? :) For this reason I want to split the preferences window from the rest of the application, and let the preferences window to run as ?independent? program. The preferences program ?should? write to a Property file(not a problem at all) and to send a "update signal" to the main program - which means it should call the update method (that i wrote) that found in the Main class. How can I call the update method in the Main program from the preferences program? To put it another way, is a way to build preferences window that take system resources just when the window appears? Is this approach - of separating programs and let them talk to each other (somehow) - the right approach for speeding up my programs?

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  • In Java, can a final field be initialized from a constructor helper?

    - by csj
    I have a final non-static member: private final HashMap<String,String> myMap; I would like to initialize it using a method called by the constructor. Since myMap is final, my "helper" method is unable to initialize it directly. Of course I have options: I could implement the myMap initialization code directly in the constructor. MyConstructor (String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... // other initialization stuff unrelated to myMap } I could have my helper method build the HashMap, return it to the constructor, and have the constructor then assign the object to myMap. MyConstructor (String someThingNecessary) { myMap = InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } private HashMap<String,String> InitializeMyMap(String someThingNecessary) { HashMap<String,String> initializedMap = new HashMap<String,String>(); initializedMap.put("blah","blahblah"); // etc... return initializedMap; } Method #2 is fine, however, I'm wondering if there's some way I could allow the helper method to directly manipulate myMap. Perhaps a modifier that indicates it can only be called by the constructor? MyConstructor (String someThingNecessary) { InitializeMyMap(someThingNecessary); // other initialization stuff unrelated to myMap } // helper doesn't work since it can't modify a final member private void InitializeMyMap(String someThingNecessary) { myMap = new HashMap<String,String>(); myMap.put("blah","blahblah"); // etc... }

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  • How to implement event listener in background of the main program in java?

    - by Johny
    Hi im a beginner so sorry for my question if it sounds naive. I want to implement a thread that runs in the background and listens all the time. By listening i mean, say it keeps check on a value returned from main thread and if the vaue exceeds certain figure, it executes some method, or say exits the program. If you could give me some idea or at least refer me to something useful, that'll be great.

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  • Is there a way to launch an aggressive and complete garbage collection in Java?

    - by Gnoupi
    For memory optimization reasons, I'm launching myself the garbage collector during profiling, to check if objects are correctly cleaned after disposing of them. The call to garbage collector is not enough, though, and it seems that there is no guarantee of what it will clean. Is there a way to call it, to be sure it will recover as much as it can, in profiling conditions (this would have no point in production, of course)? Or is "calling it several times" the only way to be "almost sure"? Or did I simply misunderstand something about the Garbage Collector?

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  • Understanding reflection

    - by sdmiller
    I recently started work at a new company and a .net web application we have is built using reflection. I have only been out of school for a year and haven't worked with this concept. After studying the code... it looks like there is a single backend interface of type object that has about 20 classes that inherit from it. lots of generic gets and sets On the surface it looks like standard inheritance to me. I guess my question is, what makes this reflection? Is it because the interface is not strongly typed? Thanks

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  • Java JIT compiler compiles at compile time or runtime ?

    - by Tony
    From wiki: In computing, just-in-time compilation (JIT), also known as dynamic translation, is a technique for improving the runtime performance of a computer program. So I guess JVM has another compiler, not javac, that only compiles bytecode to machine code at runtime, while javac compiles sources to bytecode,is that right?

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  • ASP.NET Custom Control With A Property That Is An Interface

    - by user129674
    I want to have a property on my custom control that is an interface type. For example: [ ToolboxData("<{0}:MyTextBox runat=server></{0}:MyTextBox"), ParseChildren(true, "Validation") ] class MyTextBox : WebControl { [ Category("Behavior"), Description("The validation to use"), DesignerSerializationVisibility(DesignerSerializationVisibility.Content), PersistenceMode(PersistenceMode.InnerDefaultProperty) ] public IValidation Validation { get; set; } } Then when I go to use my control in a web form I would like to be able to do: <my:MyTextBox ID="txt" runat="server"> <my:FancyValidator /> </my:MyTextBox> That way I will be able to define one class that could use any number of validators. When I try and do this now, I end up with an error saying: Type 'IValidator' does not have a public property named 'FancyValidator' What do I need to do to make this work? Thanks!

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  • How to check if String value is Boolean type in Java?

    - by Ragnar
    I did a little search on this but couldn't find anything useful. The point being that if String value is either "true" or "false" the return value should be true. In every other value it should be false. I tried these: String value = "false"; System.out.println("test1: " + Boolean.parseBoolean(value)); System.out.println("test2: " + Boolean.valueOf(value)); System.out.println("test3: " + Boolean.getBoolean(value)); All functions returned false :(

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  • Weird behaviour with Scanner#nextFloat

    - by James P.
    Running the following in Eclipse initially caused Scanner to not recognize carriage returns in the console effectively blocking further input: price = sc.nextFloat(); Adding this line before the code causes Scanner to accept 0,23 (french notation) as a float: Locale.setDefault(Locale.US); This is most probably due to regional settings in Windows XP Pro. When the code is run again 0,23 is still accepted and entering 0.23 causes it to throw a java.util.InputMismatchException. Any explanation as to why this is happening? Also is there a workaround or should I just use Float#parseFloat? Edit: import java.util.Locale; import java.util.Scanner; public class NexFloatTest { public static void main(String[] args) { //Locale.setDefault(Locale.US); //Locale.setDefault(Locale.FRANCE); // Gives fr_BE on this system System.out.println(Locale.getDefault()); float price; String uSDecimal = "0.23"; String frenchDecimal = "0,23"; Scanner sc = new Scanner(uSDecimal); try{ price = sc.nextFloat(); System.out.println(price); } catch (java.util.InputMismatchException e){ e.printStackTrace(); } try{ sc = new Scanner(frenchDecimal); price = sc.nextFloat(); System.out.println(price); } catch (java.util.InputMismatchException e){ e.printStackTrace(); } String title = null; System.out.print("Enter title:"); try{ title = sc.nextLine(); // This line is skippe } catch(java.util.NoSuchElementException e ){ e.printStackTrace(); } System.out.print(title); } }

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  • Multithreaded java cache for objects that are heavy to create ?

    - by krosenvold
    I need a cache some objects with fairly heavy creation times, and I need exactly-once creation semantics. It should be possible to create objects for different CacheKeys concurrently. I think I need something that (under the hood) does something like this: ConcurrentHashMap<CacheKey, Future<HeavyObject>> Are there any existing open-source implementations of this that I can re-use ?

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  • Can you tell on runtime if you're running java from within a jar?

    - by Dikla
    Hi, I have an application that some of my users run from Eclipse, and others run it by using a jar file. I want some actions to be done when running from within the jar, but I don't want them to be done when running from Eclipse. Is there a way to know on runtime whether the current application is running from within a jar? Thanks! Dikla

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  • java: how to make srollable panel with radio button and labels inside?

    - by Lucia
    Hi, I got a JScrollPane in which I want to place a list of radio buttons and labels. My problem is the panel doesn't scroll, I suppose it's because i didn't set a viewport, but how can I set it when I have to many components? My code looks something like this: JScrollPane panel = new JScrollPane(); JRadioButton myRadio; JLabel myLabel; for(int i = 0; i<100; i++){ myRadio = new JRadioButton(); myLabel = new JLabel("text"); panel.add(myRadio); panel.add(myLabel); } Thanks.

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  • How does transmission created it's cross plataform app? It has from Qt/Mac to CLI interfaces!

    - by Somebody still uses you MS-DOS
    I'm amazed at Transmission, a BT client. It has a Mac, a GTK+, a QT, a Web Client and a CLI interface to it. I tried reading some of it's source to understand how he creates all these interfaces, but no luck. Does the developer creates them using a single ide? Or does he create the interface logic in each specific environment (specially mac), "exports" this window code and integrates with the main logic? How did the developers create this software with so many interfaces?

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